What should you do if the onboard LAN adapter fails, preventing network connection?

When the onboard LAN adapter fails and thus disrupts the network connection, adding a Network Interface Card (NIC) using a PCI slot is an effective solution. This option provides a straightforward way to restore network connectivity without the need for extensive hardware changes or replacements.

By installing a NIC, you bypass the malfunctioning onboard adapter and can immediately regain access to a network. This is not only a relatively simple fix but also a cost-effective one compared to replacing the entire motherboard, which would involve significant effort and expense without a guarantee that other components might not also be problematic.

Using a NIC in a PCI slot allows for flexibility, as it can be chosen based on the specific needs for speed or connection type, ensuring compatibility with various network standards. This approach is commonly employed in troubleshooting network issues and provides a quick solution to restoring functionality.

The other options—replacing the motherboard, installing a new onboard LAN adapter, or removing the HDD—do not address the issue effectively. Replacing the motherboard is unnecessary and costly, installing a new onboard LAN adapter is not typically feasible if the integrated option is what has failed, and removing the HDD does not relate to network connectivity issues.